1. Field of the Invention
The present invention relates to a differential amplifier circuit and a wireless receiving apparatus, and particularly to a differential amplifier circuit including a common source circuit and a source follower circuit.
2. Description of the Related Art
In a differential amplifier circuit, a common source circuit or a common gate circuit is generally used for securing gain and a source follower circuit is generally used for securing linearity.
For example, Japanese Patent Application Laid-open No. H04-90207 discloses, for an amplifier that includes a preceding-stage amplifier circuit including a common source circuit at the first stage thereof and an output-stage amplifier circuit including a source follower circuit connected to the output of the preceding-stage amplifier circuit, a method of disposing an intermediate-stage amplifier circuit, which includes a source follower circuit with the load on the source side changed to a variable load, between the preceding-stage amplifier and the output-stage amplifier.
However, the use of a common source circuit and a common gate circuit results in poor linearity and the use of a source follower circuit results in poor gain. Moreover, if, in order to secure linearity, source degeneration is applied in a common source circuit; then it becomes difficult to perform a low-voltage operation.
Besides, since the method disclosed in Japanese Patent Application Laid-open No. H04-90207 includes multi-stage connection between the source follower circuit and the common source circuit, separate bias currents are passed to the source follower circuit and the common source circuit. That causes an increase in the amount of consumption current.